Letter from Francis Fox, 28 Victoria Street, Westminster, London, to Robert [William Frederick] Harrison, The Royal Society, Burlington House 'Dear Mr Harrison, We have fixed Wednesday February 3rd at 3.15.pm., to visit the Tube Railway at the shaft of the Brompton & Piccadilly Railway near Brimpton Oratory. May I hope to see you there at that time, and I shall be glad if you will bring any friends with you. Kindly fix a time this week when I may come up to try my hand at sketching in your optical Lantern. I am anxious to ascertain the results, as in the event of it not being successful, I shall have to prepare some diagrams which will require considerable time to make. Yours faithfully, Francis Fox'. 25 January 1904